Friday, 31 January 2014

Trial by Carbon

After half a dozen or so carved Greenland paddles I thought had it pretty much in hand. I had the dimensions sorted. I knew how the timber worked, how it smelled, how long it took to get the splinters out from under my nails, how to sand the epoxy coats back to nothing for the third time to start again. I knew how to make the shaft just thin enough to feel strong until you really needed to trust it, then that exhilarating crack as the shaft splits.

I began to hanker for a new challenge.

A couple of years ago I bought some Carbon Fibre sticks from Ron at Novorca. I had no idea how such things may be made…

This is the point at which the Imp of the Perverse habitually stirs on my shoulder and whispers into my ear the familiar words: “How hard can it be?”

Round about then I was lucky enough to paddle with Terry Hayes who had a lovely Kevlar/carbon GP he had made, and he was very forthcoming with advice and, yep, encouragement.

This was music to the Imp, and as I held Terry’s blade in my hand on the cool Clontarf sands I knew I had no choice. My course was set. I was like an arrow fired from a bow, with no choice other than to head for the target. Possibly the world’s slowest, least accurate arrow.

There are numerous blogs on the subject of making CF GP’s, and all of them basically say it’s achievable. After my previous successes, that’s a flashing red danger sign, but no. How hard can it be?

The plan crystallised in my mind: a core carved from solid balsa, sheathed in a composite sleeve and locked in layers of fragrant epoxy goodness.

Terry put me on to Soller Composites in the US, resplendent in its 1995 website design but boasting the most amazing array of composites: if you want carbon/Kevlar, rainbow-coloured glass fibre, carbon fibre honeycomb in a hundred different weights, weaves and applications, this place is for you.

Then off to the Riley Balsa Surfboards, deep in the shire. Mark Riley makes exquisite balsa-core boards but they also import balsa in big blocks. I eventually ordered a 220cm blank (three different densities on offer, these guys are serious) at $75. As I drove back with the featherlight blank strapped to the roof of my little car the Imp could barely control himself.

From my days ruining fibreglass projects I knew getting the fabric and epoxy to conform to a roundish object without sagging or air bubbles was a special hell, so I decided vacuum bagging was the way to go. I just needed something to pump the air out of a three-metre plastic bag. On an Australian specialist site you can get a pump, catchpot ( go with me on this), tubing, vacuum bag tape, clamps for a snip: just under $500 the lot. Alternatively you could buy the cheapest Chinese-made food vac-bagger you can find on ebay, a flimsy and electrically unsafe confection guaranteed to fail at the first use, for under $40. That might be cheaper but the chances of it doing the job are remote. A fool’s saving.

With my order safely placed to Hong Kong, I had everything I needed to make a start. I began to mark up the balsa blank and discovered that balsa does not cure straight, but warps severely and you have to carve the straight block out of it the blank to even begin. Half the balsa hit the floor just getting back to true. Balsa is not like the other wood I’ve worked. It’s fibrous, tenacious, uncooperative. It jams up a plane and when sanded it forms fine floating flakes and dust that look like they would just love to settle deep down in your lungs. It has an aggressive grain that loves to split. After a few frustrating hours I discarded the plane, whetted the kitchen knife and went to work with that.

The blade eventually emerged. Finishing off with the trusty power sander: our back yard and the neighbours’ became a winter wonderland of soft blonde powder. For months afterwards.
At about that time the coil of CF sleeve arrived with a cheery note from Soller. It was slippery, lustrous and graphite-coloured, soft and supple to hold, nothing like the coarseness of glass fibre. This seductive stuff looked like fun to work with.

Also arriving in the mail was the unimpressive Chinese food bagger, with a useful three-metre length of plastic bag. I named it after Bilbo Baggins’ little-known useless brother Lamo. And all this time the Imp never left my shoulder. How hard could it be?

I had all the equipment, a fully carved balsa blade, a few litres of epoxy, and a weekend ahead. Everything was ready.

Five months later I finally got sick of being nagged by the bare balsa paddle every time I went to the cupboard. The Imp, who had grudgingly been snoozing for months, woke immediately.

I knew that once I got started, I would have to keep going to the end, so I covered the kitchen in drop sheets, set out a dozen vinyl disposable gloves, the crappy food bagger, some robust plastic beakers to mix the resin and of course the slick sleeve of carbon. It was like a cut-rate scene from Dexter.

The first thickness of the sleeve went on smoothly. The Imp had a firm opinion that I should wet the first CF layer before sliding on the dry second: but the prospect of dealing with a wet, slippery 2.5m resin-coated paddle while trying to slide a second sleeve over it was a too much, and I opted to do both layers dry. Strange sort of task, like sliding a snake back into its skin. With each layer I smoothed it tight from the centre, a curiously satisfying tactile experience but one which resulted in quantities of fine wool-like carbon fluff, looking like the friendliest carcinogen in town ( after fine balsa dust).

Then into it with the resin. Slop, slop, slop, shoo the dog out of the way, bugger it’s walked through the drips and headed for the carpet, nothing to be done, work the resin into the fibre and hope it penetrates. With a beautiful two-metre sodden stick oozing epoxy goodness all over the landscape I belatedly work out how to get it into the narrow 2.5 m plastic bag. It obviously won’t just pull up over the stick, that will force the wet fibre up the blade – so off with the gloves and turn the bag inside out. On with new gloves, gradually envelope the stick with the bag like a starfish extruding its stomach, stick a bit of old towel in the top of the bag to catch excess resin before it gets into the vacuum device. Gloves off, then lay the top of the bag in the gate of Lamo Baggins.

This is where I discover Lamo has several functions ( seal, suck, cut etc) with just one unmarked button and no instructions. I work my way through the possibility space ( seal/not suck, cut /not seal, suck /not seal, suck /not cut) each time using up a bit more of the extra half metre of the bag until just as I reach my bit of old towel I hit the suck, seal, cut combo.

Forty minutes of wheezy sucking noise later (the machine, not me) and the bag seems no more evacuated than the start. The resin is starting to go off, I can tell because the dog’s footprints are getting very tacky in the carpet. Come to think of it the dog has been standing still in one place for an unusually long time, looking plaintive. Tentatively I undo the bagger and find I wasn’t quite so smart after all, didn’t quite get the suck/seal/cut thing working. More fiddling, at last it starts sucking toxic fumes out of the bag and pumping them into the kitchen. Success!

A day later, after the resin has finally gone off and I’ve chipped the dog free, I cut the blade out of the bag. The edges are razor sharp where the resin has oozed out in a thin sheet and have no trouble cutting through the plastic dropsheet and the tablecloth underneath in one go. The Imp is well satisfied.

The next weekend is a blur of additional resin coats and power sanding ( a whole now world of toxic dusts, now with added carbon fibre goodness) as I gradually fill in the depressions and sand down the inexplicable bumps until the blade starts to feel smooth. The third coat of resin goes on strangely and takes almost a week to go off, leaving a slightly creepy leprous quality to the finished blade. Finally I’m down to the final fibreglass polish: rubbing furiously with a cloth. Just the thing for the recovering tennis elbow.

Then it’s done. For about a hundred and sixty bucks I have an imperfectly shaped GP that seems to have a nasty rash, but it feels light and it even works well in the water. The Imp, sad to say, lost interest as soon as things started to go well, and has gone back to sleep until the next challenge. I’ve got a couple of litres of resin I have to find a use for within the year, a dog who seems to have forgiven me now that the hair on her feet has grown back, Lamo Baggins now resolutely sealed shut by to the resin it sucked into its works, and a tablecloth with a stylish slash in it. I have learned that balsa is an uncooperative timber best left alone, that multiple coats of resin multiplies the unpredictability of the end result and that the thing that’s used up most is time.